Sepsis is a serious and potentially lethal pathological condition of the body resulting from the presence of infectious microorganisms. This condition clinically manifests as one or more of the following sequelae: pyrexia (fever), hypotension (low blood pressure), hypoxemia (low blood oxygen tension), tachycardia (elevated heart rate), hypothermia (decreased body temperature), neutrophilia (increased numbers of circulating neutrophils), and neutropenia (decreased numbers of circulating neutrophils). While these sequelae individually may have profound effects on normal body physiology, in excess or in combination they lead to an acute pathological state called shock, which is often fatal if not treated rapidly and aggressively. For example, hospital and particularly intensive care unit patients who have acquired nosocomial infections as a result of peri- or post-operative immunosuppression or secondary to other disease processes, such as pancreatitis, hypotensive or hypovolemic shock, physical trauma, burn injury, or organ transplantation, and develop septic shock syndrome have a mortality which has been quoted to range from 30-70% depending upon other co-incident complications.
Treatment of sepsis patients is not straightforward. Depending on the specific stage of sepsis and the corresponding status of the patient's immune system, a particular treatment may be ineffective or even exacerbate the patient's condition. Early in sepsis, when circulating microorganisms are present, the most appropriate treatment is that directed specifically against microorganisms and microbial products, such as antibiotic or anti-microbial toxin therapies, including anti-lipopolysaccharide (LPS) antibodies, polymyxin derivatives, and synthetic HDL. At this stage, the patent's immune system is only slightly compromised. Once the level of microorganisms and their toxic products has increased, microbial cell products stimulate the body's white blood cells to secrete inflammatory mediators, such as tumor necrosis factor (TNF) and interleukin-1 (IL-1), which are responsible for many of the early sequelae and symptoms of sepsis. At this stage, antibiotic and anti-microbial therapies are less effective, and the patients should be treated with agents to inactivate inflammatory mediators, such as anti-cytokine antibodies, interleukin receptor antagonists, TNF receptor, pentoxyphylline, or anti-inflammatory cytokines such as interleukin-11 (IL-11). At this stage the patient's immune system is in a hyperactivated state. Further progression of sepsis leads to a severe decline in the immune responsiveness of the patient, a condition called anergy, in which the immune system fails. The patients white blood cells are increasingly unable to destroy microorganisms. At this stage, both of the aforementioned therapies are mostly ineffective and the patient must be treated with immune system stimulants, such as glutamine, non-steroidal anti-inflammatory agents, granulocyte colony stimulating factor, betafectin, and interleukin-11 (IL-11) in order to rescue the patient from impending demise. Thus, without knowing the stage of sepsis, appropriate treatments may be ineffective or withheld, contributing to the eventual demise of the patient.
Furthermore, despite the development of increasingly potent antimicrobial agents, the incidence of nosocomial infections and in particular, infections leading to sepsis or septicemia, is increasing. The difficulty with many of the promising therapeutic agents is that their window of opportunity and indications for use have not been adequately delineated largely due to a lack of appropriate rapid and quantitative diagnostic procedures and partly due to a lack of complete understanding of the pathogenesis of the sepsis syndrome. For example, until the recent advent of novel therapeutic strategies, sepsis patients have been managed largely by palliative care and administration of antibiotics. The biotechnology industry has facilitated the large scale production of many new targeted biopharmaceuticals which utilize monoclonal antibodies against such initiators of sepsis as gram-negative endotoxin (Centocor's HA-1 A(R) or Xoma's Xomen-E5(R)), tumor necrosis factor (various producers including Hoffman La Roche and Centocor with patents WO 90/06514 and WO 92/16553), interleukins, as well as various soluble receptor antagonists such as IL-1 RA (Synergen) and sCR.sub.1 (soluble complement receptor 1)--a truncated recombinant complement regulatory molecule. The cost of these therapeutic agents is significant, being priced at $3,000.00 to $4,000.00 per dose. Thus, providing this therapy indiscriminately to patients would add a considerable burden to the health care system without providing a corresponding benefit to patients.
Notably absent from the physician's diagnostic armamentarium is a method and diagnostic test to easily and rapidly determine the patient's stage of sepsis at a specific time, so that the appropriate therapy may be initiated. Staging sepsis requires knowledge of several factors, including the level of microbial products in the patient's blood and the status of the patient's white blood cells. Presently these assessments may be made utilizing several diverse methods and test procedures. Centocor Inc.'s immunometric assay for tumor necrosis factor-alpha (TNF-.alpha.), as described in WO 90/06314, uses two antibodies, one of which is labeled, to measure the level of this inflammatory mediator. The National Aeronautics and Space Administration detects Pseudomonas bacteria by extraction of Azurin and detection using Azurin-specific antibody (U.S. Pat. No. 5,210,019). The endotoxin assay kit from BioWhittaker (Walkerville, Md., U.S.A.) or Seikagaku Kogyo Ltd. (Tokyo, Japan) is a Limulus Amebocyte Lysate (LAL) Assay technique also measure levels of endotoxin. Stevens et al. (J. Infect. Disease 170:1463-1472, 1994) provide a complex automated method for determining phagocyte function utilizing several measures: phorbol myristate acetate (PMA)-stimulated oxidase activity, PMA-stimulated simple dioxygenation, and circulating and primed opsonin receptor-dependent dioxygenation activity. These data provide a measure of the state of circulating phagocytes, which represents incomplete information for determining the stage of sepsis of the patient.
Copending application Ser. No. 08/552,145 now U.S. Pat. No. 5,804,370 and Ser. No. 08/516,204 now abonded, incorporated herein by reference, describe methods that may be used to indicate the presence of microbial products in a patient's blood sample by first forming an immunocomplex between the preselected microbial product and an antibody thereto which is added to the sample. Any immunocomplex formed as a result then activates complement present in the blood sample which in turn causes neutrophils and other white blood cells present in the blood sample to produce oxidants. The oxidants then cause an added chemiluminogenic compound, such as luminol, to release light energy. The white blood cells optionally may be stimulated through the addition of opsonized zymosan or other agents resulting in increased production of oxidants. The amount of light emitted over time may be measured by a luminometer device to indicate the presence of the microbial product in the sample. A control sample without the addition of antibody is included, to which is also added any additional stimulatory agents. This method provides a semi-quantitative determination of the level of the pre-selected microbial product in the blood sample.
Copending and concurrently filed application Ser. No. 08/991,230, incorporated herein by reference, is an improvement of the aforementioned applications in that an analyte such as endotoxin or other microbial product present in a patient's blood sample may be quantitated by combining the procedure described in the aforementioned applications with a measurement of the maximum response of the patient's white blood cells to a maximum stimulatory level of immunocomplexes. Because the level of analyte in the sample is directly related to the ratio of the chemiluminescent response from the analyte-formed immunocomplexes to the chemiluminescent response to a maximum stimulatory dose of immunocomplexes, the analyte may be quantitated in a patient's sample containing analyte and white blood cells.
It has now been found that the stage of sepsis in a patient may be determined rapidly and accurately from a sample of blood by determining microbial product levels in the sample, concurrently with an assessment of several white blood cell functions.